The present invention relates to warewashers such as dishwashing machines, and more particularly to warewashers in which the food ware items are sanitized chemically rather than thermally.
Prior art warewashers employing chemical sanitization are well-known in the art. A recent example of such a machine is shown in U.S. application Ser. No. 835,197, filed Sept. 21, 1977, assigned to the assignee of the present invention. Earlier examples of such machines may be found in U.S. Pat. Nos. 2,592,884, 2,592,885, 2,592,886, 3,044,092, 3,146,718, and 3,370,597, all assigned to the assignee of the present invention. Such machines potentially provide significant energy economies since they can satisfy sanitization standards by destroying bacteria with relatively low-temperature (approximately 120.degree.-140.degree. F.) chemically sanitizing rinse solutions, rather than requiring high temperature rinse water at 180.degree.-195.degree. F. Although the potential energy savings of chemical sanitization is significant, the design of systems which can both clean acceptably, and also reliably and consistently mix the sanitizing agent into the rinse water in the proper concentration, to assure both consistent and effective cleaning and sanitizing of the food ware items within the warewasher, has proved difficult.
The above-noted U.S. application Ser. No. 835,197, discloses a machine which provides excellent washability and also has a durable and consistently reliable mechanical delivery system for the sanitizer, assuring satisfactory operation even in highly demanding commercial applications. Even a reliable mechanical system, however, may not provide a comfortable assurance that the food ware items are being properly sanitized. That is, sooner or later the supply of the sanitizing agent will be exhausted. At that time, even though the mechanical operation of the warewasher is correct, proper sanitizing depends upon replacement of the chemical sanitizing agent. It is therefore desirable to alert the machine operator when replacement is necessary.
It is also an unavoidable fact that even the best of systems may fail. For example, a pinch in the sanitizer supply tubing (which is often exposed outside the warewasher), or some other obstruction, might impede flow of the sanitizing agent even though the supply bottle was full. It is therefore desirable to do more than simply indicate that the supply of sanitizing agent is exhausted. Preferably, an indication should be provided upon failure of proper delivery of the sanitizing agent. Then, if the warewasher is mechanically reliable, it can be assumed within acceptable design limits that proper delivery of the sanitizing agent to the warewasher is equivalent to proper sanitizing of the food ware items which are being washed.
Of course, detectors for indicating the presence, absence, or quantity of fluid within a container are well-known. Similarly, the prior art shows many flow detectors. As indicated, however, the former, while relatively inexpensive, would not really indicate or test for delivery of the sanitizer. The latter could be inserted in the sanitizer delivery conduit, but generally require sophisticated and expensive components. A need thus remains for an uncomplicated, inexpensive method and apparatus for monitoring and verifying delivery of the liquid chemical sanitizing agent to the warewasher rinse system.